Method of making a magnetic core



Jam 1965 K. D. BEARDSLEY ETAL 3,164,889

METHOD OF MAKING A MAGNETIC coma Qriginal Filed Oct. 10, 1958 UnitedStatesPatent This invention relates to a method of making a packetmagnetic core. More particularly, the invention is an improvement overthe packet magnetic core and method of making the same described andclaimed in co-pending Treanor patent applications Serial Number 712,135,now

Patent No. 3,025,483, issued January 2 3',-1962,;and.392,-

205,.issued November 22, 1960, as Patent Number 2,960,- 756 which areassigned to the same assignee as the instant patent application. By theterm packet core is meant one which has a plurality of radially nestedcurved laminations or turns which are cut into segments with a pluralityor bundle of segments of the core being simultaneously laced through theopeningof a preformed electrical coil assembly.

This application'is a division of co-pendingparent application SerialNo. 766,488, filed October 10, 1958, now Patent No. 3,074,038 issuedJanuary 15, 1963. The article described in this application is claimedin said parent application.

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter which we regard as ourinvention, it is believed the invention will be better understood fromthe following description taken in connection with the accompanyingdrawing in which:

FIGURE 1 is an elevation view of a magnetic core constructed inaccordance with one form of our invention,

and

FIGURE 2 is an exploded perspective view of the outer packet and twoturn segments of FIG. 1. l

The magnetic core illustrated in the drawing comprises a plurality ofradially nested packets l to 4. The turns or lamination of the packetsare spirally arranged andare cut into segments having a length ofapproximately one turn of the core. Preferably, the joints (see FIG. 2)of all the packets are arranged on the side of the core which will bepositioned in the opening of a not shown preformed electrical coil. Thisis so as to minimize distortion of the laminations of the corewhentheyare being laced with an electrical coil. In the particular embodiment ofthe invention illustrated in the drawing the segments of the packetshave a length of slightly more than one turn of the core.- However, aswill be obvious to those skilled. in the art and is more particularlyexplained in the copending Treanor patent applications, the segmentscould have a, length slightly less than one full turn of the core.

mately two turns of the core; Prior art magnetic cores which utilizepackets do not have such extra length segments between packets and onthe inside and outside of the core. The special segments provide severaladvantages. v

In our invention additional structuralstrength is provided in the coreinasmuch as the two turn segments hold the core together. Additionally,the amount of l'ooseness in the core is no longer critical inasmuch asthe packet joints are held snugly closed by the two turn pieces even inan excessively loose core. The two turn inner piece 8 which defines thespace or window opening in the corev holds in the insulation on the notshown electrical coil assembly and thereby provides a good base on whichto build the core. A two turn piece over each packet holds its jointsclosed whereas a clamping band'or the like on the outside of the corewould not accomplish this in the inner packets. Additionally, duringlacing of the packets without the two turn segments there is a danger ofdislodging the joints in previously laced packets. This is avoided wheneach packet is held closed bya two turn piece. 7

The preferred method of making the magnetic core is to take a strip ofpreferably grain oriented core material and wind it continuously into aplurality of radially superimposed turns on a generally rectangularshape mandrel.

Winding the core strip on a rectangular shape mandrel gives themthe-configuration desired in the final core.

After the desired number of turns are wound on the mancould be cut byunwinding it from the outside and cutting Successive layer joints whichare indicated by X marks turbance of'fiux in an adjacent layer and alsoto facilitate a simultaneous lacing of the cut segments of each packetdisturbance of flux in one layer will not effect thediswitha,preformedelectricalcoil'with minimum distortion of thelaminations In our invention, adjacent packets are separated bylaminations 5 to '7 which have a length of approximately two turns ofthe core. Also, the innermost and outermost segments 3 and. 9 of thecore have alength of approxiit from the outside to the inside. However,this means that the'whole core must be out before any of the segmentscan be laced; If the core is cut from the inside to the outside then thepackets can be laced witha pre- 7 formed electrical coil without waitinguntil the whole core has been cut; After the inner segment 8 is cut itcan be laced with the electrical coil. As the segments of the firstpacket 1 are out they are set aside in a radially nested bundle. Whenall the segments of the first packet I; are cut then the packet can beopened and laced with an electrical coil. Thereafter the next two turnsegment 5 is laced with the electrical coil to hold the joints of thefirst packet 1 closed. This procedure is continued until all the packetsand segments of the core are laced with the electrical coil and the lastpacket and whole core is finally closed by the last two turn segment 9.In our invention the'single turn segments of the packets do 'notnecessarily have to be set aside and then laced as a group but eachsingle turn segment could be individually laced with the core rightafter it has been cut. However, even with such a procedure the two'turnsegments still provide the aforementioned advantages. Additionally, ifthe core has a very'small window opening which providesinsufticientspace for the cutting tool to operate on the core from theinside to the outside, the rectangular shaped core can be expanded intosay an octagon whichwill pro vide more working space inside the corefor'the cutting tool. However, even with such an arrangement the extralength segments between packets and on the inside and outside of thecore still provides the heretofore discussed advantages of ourinvention;

Patented Jan. 12, 1965 It will be obvious to thoseskilled in the:artthat the I special segments between packets and on'theiinside and:outside of the more do not necessarily have to have a' length of twoturns of the core but can be somewhat shorter or longer than two turnsof the core. For instance, the extra length segments could have a lengthof 1 /2 turns of the core and the joints in successive packets could belocated on opposite sides of the core. The important thing to beconsidered in selecting the exact length of the special segments is thatthey be long enough to accomplish the purposes and advantages heretoforeset forth. They could be more than two turns long. However, it ispreferred not to make them too long since long segments are moredifficult to assemble with the electrical winding than short segments.Therefore, by the term about two turns long is meant segments which aresomewhat shorter or longer than two turns long which will satisfy theabove set forth requirements.

While there has been shown and described a particular embodiment of theinvention, it will be obvious to those skilled in the art that changesand modification may be made without departing from the invention, andtherefore, it is intended by the appended claims to cover all suchchanges and modifications as fall within the true spirit and scope ofthe invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. A method of making a curved magnetic core which comprises winding astrip of magnetic core material into a core form having a plurality ofradially superposed turns, clamping said core form, annealing said coreform to give said turns a permanent set, cutting said strip from theinside to the outside, without unwinding, into groups of successiveapproximately single turn length segments which are alternated withapproximately two turn length segments, and lacing said groups and twoturn segments in the order out with a preformed electrical coil.

2. A method of making a curved magnetic core' which comprises winding astrip of magnetic core material into a core form having a plurality ofradially superposed turns, clamping said core form, annealing said coreform to give said turns a permanent set, cutting said strip from theinside to the outside without unwinding alternately 4 into anapproximately two turn length segment and then a group of approximatelysingle turn length segments, radially nesting each group of single turnsegments into a packet, and alternately lacing each two turn segment andsimultaneously the single turn segments of each packet in the order cutwith a preformed electrical coil.

3. A method of making a curved magnetic core which comprises winding astrip of magnetic core material into a core form having a plurality ofradially superposed turns, clamping said core form, annealing said coreform to give said turns a permanent set, cutting said strip to provide asegment having a length of approximately two turns of said core, thencutting said strip into a plurality of segments having a length ofapproximately one turn of said core, then cutting another segment havinga length of approximately two turns of said core, again cutting aplurality of segments of approximately one turn in length and anothersegment of approximately two turns in length, and lacing said cutsegments with a preformed electric coil, by first lacing the smallest ofsaid two turn segments, then lacing all of the smallest of saidplurality of one turn segments, then lacing the next largest of said twoturn segments, then lacing all of the next largest of said plurality ofone turn segments and finally lacing the largest of said two turnsegments.

4. A method of making a curved magnetic core as claimed in claim 3 inwhich said strip is cut from the inside of said core to the outsidewithout unwinding and said segments are laced with said preformedelectric coil in the order in which they were cut.

References Cited by the Examiner UNITED STATES PATENTS 2,305,650 12/42Vienneau 29155.57 2,960,756 11/60 Treanor 29155.57 X 3,008,222 11/61Steinmayer 29-15557 JOHN F. CAMPBELL, Primary Examiner.

WHITMORE A. WILTZ, Examiner.

3. A METHOD OF MAKING A CURVED MAGNETIC CORE WHICH COMPRISES WINDING ASTRIP OF MAGNETIC CORE MATERIAL INTO A CORE FROM HAVING A PLURALITY OFRADIALLY SUPERPOSED TURNS, CLAMPING SAID CORE FORM, ANNEALING SAID COREFORM TO GIVE SAID TURNS A PERMANENT SET, CUTTING SAID STRIP TO PROVIDE ASEGMENT HAVING A LENGTH OF APPROXIMATELY TWO TURNS OF SAID CORE, THENCUTTING SAID STRIP INTO A PLURALITY OF SEGMENTS HAVING A LENGTH OFAPPROXIMATELY ONE TURN OF SAID CORE, THEN CUTTING ANOTHER SEGMENT HAVINGA LENGTH OF APPROXIMATELY TWO TURNS OF SAID CORE, AGAIN CUTTING APLURLITY OF SEGMENTS OF APPROXIMATELY ONE TURN IN LENGTH AND ANOTHERSEGMENT OF APPROXIMATELY TWO TURNS IN LENGTH, AND LACING SAID CUTRSEGMENTS WITH A PREFORMED ELECTRIC COIL, BY FIRST LACING THE SMALLEST OFSAID TWO TURN SEGMENTS, THEN LACING ALL OF THE SMALLEST OF SAIDPLURALITY OF ONE